The present invention is directed to a fuel injection control system and method. More particularly, the present invention is directed to a system and method for controlling a hydraulically-actuated fuel injector.
Environmental concerns have made the reduction of emission an important factor in the design and control of an internal combustion engine. One method of reducing the emissions generated by an internal combustion engine involves precisely controlling the timing and amount of fuel injected into the combustion chambers of the internal combustion engine.
An internal combustion engine may include a fuel injection system that injects fuel to the combustion chambers. The fuel injection system typically includes one fuel injector for each combustion chamber. The fuel injectors may be, for example, hydraulically-actuated electronically-controlled unit injectors. This type of fuel injector dispenses a quantity of fuel into the combustion chamber of the engine based on the controlled introduction of a pressurized fluid, which pressurizes the fuel to injection pressure.
The internal combustion engine may also include an electronic control module (xe2x80x9cECMxe2x80x9d) that controls each fuel injector to deliver a certain quantity of fuel to each combustion chamber at a certain time in the operating cycle. The ECM may generate and apply an injection signal to each fuel injector to deliver a quantity of fuel to each combustion chamber. In the case of a hydraulically-actuated electronically-controlled fuel injector, the injection signal may be a current applied to a solenoid in the fuel injector. The current energizes the solenoid to open a valve, which allows the pressurized fluid to flow through the fuel injector and pressurize and deliver fuel to the combustion chamber. The magnitude and duration of the current determines the amount of fuel delivery.
Because the pressurized fluid is integral to the operation of the fuel injector, the properties of the pressurized fluid may impact the amount of fuel delivered for a given injection signal. For example, if the pressurized fluid has a relatively high viscosity, the amount of fuel delivered for a given injection signal may be different than the amount of fuel delivered when the pressurized fluid has a relatively low viscosity. Accordingly, the ECM may use the properties of the pressurized fluid as an input in determining the magnitude and duration of the injection signal.
As described in U.S. Pat. No. 6,102,004, the ECM may use the pressure of the pressurized fluid and the temperature of the engine as inputs when generating the injection signal. Based on these parameters, the ECM accesses a series of xe2x80x9ccalibration mapsxe2x80x9d that store data for the fuel injector. These calibration maps provide information on the required duration of the injection signal to achieve the desired fuel delivery amount given the particular operating conditions. Thus, the ECM may generate an appropriate injection signal based on the pressure of the operating fluid and the temperature of the engine.
However, generating these calibration maps may be an expensive and time-consuming process. Each fuel injector must be calibrated with each different type of operating fluid that may be used to operate the fuel injection system. This entails testing the fuel injector under a variety of pressure and temperature conditions for each different type of operating fluid.
In addition, this type of fuel injection control system does not provide for any feedback on the fuel injection process. The ECM is not able to determine if there is a difference between the desired amount of fuel delivery and the actual amount of fuel delivery. If there is a significant difference, such as, for example, too much fuel is delivered to the combustion chamber, the engine may generate excessive emissions and/or experience xe2x80x9croughxe2x80x9d running conditions. The current fuel injection control systems do not provide for the correction of future fuel injections based on fuel delivery discrepancies in past fuel injections.
The fuel injection control system of the present invention solves one or more of the problems set forth above.
One aspect of the present invention is directed to a method of controlling a fuel injector. A first injection signal is applied to a hydraulically actuated fuel injector to inject a quantity of fuel into a combustion chamber of an internal combustion engine. An amount of an operating fluid used by the fuel injector to inject the quantity of fuel into the combustion chamber is calculated. The amount of fuel injected into the combustion chamber is estimated based on the amount of operating fluid used by the fuel injector. A viscosity parameter is determined for the fuel injector based on the duration of the first injection signal and the estimated amount of fuel injected into the combustion chamber.
In another aspect, the present invention is directed to a fuel injection system. The fuel injection system includes a fluid supply rail configured to conduct a pressurized fluid. A fuel injector having a valve is configured to introduce an amount of pressurized fluid into the fuel injector from the fluid supply rail. The fuel injector is configured to release an amount of fuel in response to the introduction of the pressurized fluid. An electronic control module is configured to apply a first injection signal to the fuel injector to modulate the valve, to calculate the amount of pressurized fluid used by the fuel injector, to calculate an amount of fuel injected into the combustion chamber based on the calculated amount of pressurized fluid used by the fuel injector, and to determine a viscosity parameter indicating the sensitivity of the fuel injector to the properties of the pressurized fluid.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.